The present disclosure relates to a power supply apparatus, a power controlling system and a starting method for an electric apparatus. Particularly, the present disclosure relates to a power supply apparatus, a power controlling system and a starting method for an electric apparatus for converting an input voltage from an electric generator whose terminal voltage exhibits a fluctuation such as a solar cell and supplying the voltage obtained, by the conversion to a load.
In recent years, attention is paid to natural energy, also called clean energy, which emits no air pollution offender upon electric power generation.
The natural energy is electric power obtained, for example, by photovoltaic power generation, solar thermal power generation, wind power generation or the like. Also it is attempted actively to extract electric energy from kinetic energy generated by human activities although the generated power is low in comparison with that by photovoltaic power generation and so forth.
Incidentally, electric power obtained from an electric generator which converts natural energy into electric energy fluctuates by a great amount in response to a surrounding environment. For example, in the case of photovoltaic power generation, obtained generated electric power sometimes fluctuates suddenly in response to a variation of the illumination intensity on the solar cell, a variation of the temperature or the like.
Therefore, in order to efficiently and stably extract electric power from a solar cell, it as a common countermeasure to interpose, between the solar cell and a load, a power conditioner which includes a converter for converting an input voltage into another suitable voltage and out putting the voltage obtained by the conversion.
Incidentally, upon starting up of the power conditioner interposed between the solar cell and the load, certain fixed power is supplied to the power conditioner in order to start up the converter. For example, in the case of a configuration wherein power required for starring up of the converter is supplied from the solar cell, the converter cannot be started up where the generated electric power amount of the solar cell is small. Therefore, the power conditioner itself cannot be started up and electric power cannot be extracted from, the solar cell.
Particularly, if a capacitor having high capacitance is interposed between the solar cell and the converter, then when the power conditioner is connected to the solar cell, rush current to the capacitor appears and the terminal voltage of the solar cell suddenly drops. If the terminal voltage of the solar cell drops suddenly, then the power conditioner cannot be started up with the electric power obtained from the solar cell.
Japanese Patent Laid-Open No. 2011-193633 discloses a power conversion apparatus wherein a direct current side capacitor is charged up in advance by an initial charging circuit which converts AC power from an electric power system into DC power and then a linkage switch is switched on to suppress rush current appearing in a starting up process. Meanwhile, Japanese Patent Laid-Open No. 2009-038967 discloses a boosting apparatus which includes a boosting circuit in which a first solar cell for generating electric power for a load such as a secondary cell and a second solar cell are connected to each other. In the boosting apparatus, starting up energy for the boosting circuit is supplied from the second solar cell connected in series to the boosting circuit.
Further, Japanese Patent Laid-Open No. 2010-226917 discloses a switching power supply apparatus wherein the rate of change of the duty of a switching element is changed so that the period of time for starting up may be fixed based on a signal which is set by detecting an input voltage and is used to set the on-duty upon starting up. Furthermore, Japanese Patent Laid-Open No. 2011-125132 discloses a switching power supply wherein, if an input voltage reaches a predetermined voltage, then charge of a capacitor connected between terminals of a tertiary winding is started. Then, a starting up switch circuit is switched on after lapse of a predetermined period of time after the starting of the charge of the capacitor.